Example of infix operator overload in Swift

Operator.swift

struct Vector
{
    var x: Double = 0
    var y: Double = 0

    init(x: Double, y: Double)
    {
        self.x = x
        self.y = y
    }
}

// v0 = v1 + v2
func +(left: Vector, right: Vector) -> Vector
{
    return Vector(left.x + right.x, left.y + right.y)
}

// v1 += v2
func += (inout left : Vector, right: Vector)
{
  left.x += right.x
  left.y += right.y
}